Zeolites, especially those of the zeolite A type, are commonly employed as builders in detergent compositions. They have largely replaced the use of the more conventional polyphosphates. Their advantages lie not only in their high calcium binding capacity, but also and in particular in their high ecotoxicological compatability.
Zeolites are typically manufactured from in the form of an aqueous suspension which may either be stored and marketed as such or may be subjected to spray drying. Zeolites have extremely poor solubility in water, so that suspensions of zeolites readily sediment. In the most favorable case, this leads to phase separation although, normally, considerable quantities of the solid sink to the bottom of the vessels in storage, harden and have to be subsequently removed, size-reduced and re-suspended which results in the expenditure of considerable amounts of time, effort and finances. In other cases, the viscosity of the suspensions increases to such an extent that transfer to another vessel or circulation by pumping is difficult, if not impossible, and in any event involves considerable product losses.
There has been no shortage of attempts in the past to stabilize aqueous zeolite suspensions in such a way that they remain stable in storage for a sufficient time and can be transported through pipes without blocking them.